The present invention relates to devices and methods for minimizing air entrapment when dispensing fluids, more particularly for dispensing fluids into small diameter, elongated reservoirs.
When a fluid is dispensed into a small diameter tube, such as the reservoir of a pen, the relatively small clearance between the filling tube and the wall of the reservoir will in some cases tend to cause the fluid to rush up the sides of the reservoir, fouling the filling tube. In other cases, turbulence in the fluid may cause air to be incorporated into the fluid. Additionally, the fluid may not reach the bottom of the tube, leaving an air pocket in the bottom of the tube.
In the case of filling ink into a pen reservoir, if this air pocket is at the writing end of the pen it may prevent the pen from functioning. The air entrained in the ink can also have a deleterious effect on pen performance. Therefore, it is often necessary to centrifuge the filled pens to remove entrapped air. Ball point pens are often manufactured by filling the pen reservoir completely, with the tip area of the pen open, and centrifuging the pen prior to applying the ball point.